Rare Cholera Outbreak Hits Vancouver Island, Canada

The First Nations Health Authority (FNHA) and Island Health are currently investigating a rare cholera outbreak on Vancouver Island, Canada, which has been linked with the consumption of herring eggs.

In a warning to the public on March 22, 2018, officials stated that 3 individuals were confirmed to have cholera, a water-borne disease that is usually acquired via the consumption of food or water contaminated with the bacteria Vibrio cholerae.

Although rare in the United States, according to the Centers for Disease Control and Prevention (CDC), cholera cases have been on a steady climb globally since 2005. In fact, the World Health Organization (WHO) estimates that about 1.3 million to 4 million individuals fall ill with the disease each year, and about 21,000 to 143,000 die. In the last 5 years, WHO has reported only 7 cases in Canada.

Officials warned that herring eggs harvested specifically in the French Creek to Qualicum Bay area were associated with the infections. “These cases are only associated with herring eggs laid in the marine environment, and not herring roe which is harvested directly from the fish,” officials shared in a March 23rd update. As such, the Department of Fisheries and Oceans called for an emergency closure on herring egg harvest in Mid-Vancouver Island.

In a subsequent update released on March 29, officials reminded harvesters to check area closures before harvesting bivalves as a way to prevent illness and urge the public to stay away from consuming any herring eggs harvested from the French Creek to Qualicum Bay area.

The most recent notice, released on April 6, a confirmation that the bacteria were found not only in herring eggs but also in water samples collected from the French Creek and Qualicum Bay closure areas. However, no other cases had been reported.

Brackish and marine waters are known to serve as a natural environment for cholera, as well fecal-contaminated wastewater. In fact, a report released by the Canadian Broadcasting Center in 2015 found that 12.7% of wastewater in the province where Vancouver Island is located had gone untreated. Furthermore, upwards of 41 billion liters of untreated sewage had been dumped in nearby waters, “including nearly 17 billion liters off the coast of Vancouver, British Columbia, which is directly across the Strait of Georgia from Vancouver Island,” according to the Outbreak Observatory. Thus, fecally-contaminated water could have potentially contributed to the contamination of the herring eggs.

Several other factors could be playing a role in the outbreak as well, according to the Outbreak Observatory. Excess water brought on by unusually heavy rainfalls could work to “overwhelm” water treatment facilities, which might be unable to handle the excess volume of water, and thus, untreated water could make its way into the environment. A past study examining the relationship between increased rainfall and cholera incidence, found heavy rainfall to be associated with an increase in cholera risk 4 to 7 days later.

A change in climate could also potentially play a role. An association between V. cholerae and chitinaceous zooplankton and shellfish has been documented in past research, and as temperature rises, plankton blooms are typically witnessed. Tidal currents could be working to spread these bacteria as the plankton blooms are spread along coastal areas.

“While lab-identified V. cholerae infection is rare on the West Coast, viruses and bacteria are a known risk from eating raw seafood,” The FNHA and Island Health stressed in the most recent update. FNHA and Island Health will release more information pertaining to the investigation as it is made available.

Contagion® is a fully integrated news resource covering all areas of infectious disease. Through our website, quarterly journal, email newsletters, social media outlets, and Outbreak Monitor we provide practitioners and specialists with disease-specific information designed to improve patient outcomes and assist with the identification, diagnosis, treatment, and prevention of infectious diseases. Our mission is to assure that the healthcare community and public have the knowledge to make more informed choices and have a positive impact on patient outcomes.